The present invention broadly relates to the continuous casting art, and, more specifically, concerns a new and improved method of continuously casting metals, especially steel, wherein steel is cast into a continuous casting mold having at least two taper stages or regions which follow one another in the direction of travel of the cast strand, and furthermore, this invention also concerns apparatus for the performance of the aforesaid method.
The shrinkage behavior, during the casting of steel strands having the same cross-section, is dependent upon the casting parameters, such as the composition of the melt, the casting speed, casting temperature and casting process, such as for instance whether casting is accomplished with or without flux powder. During the production of continuously cast strands frequently the taper of the continuous casting mold is accommodated to the shrinkage behavior of different steel qualities and the contemplated casting speed. Apart from thereby achieving a reduced tendency of metal break-out there is furthermore obtained optimum cooling of the strand, which, in turn, ensures for good quality of the cast strand product.
During the continuous casting of steel billets and blooms it is known from practice to use tube molds having an appropriately conically configured hollow mold cavity or compartment. On the one hand, the taper thereof is accommodated to the strand or cross-section and, on the other hand, to the steel quality as well as the contemplated mean or average casting speed. If, for instance, the steel quality is altered from conventional carbon steels to austenitic or other alloyed steels, then the different shrinkage behavior of these two types of steels is taken into account by exchanging the mold for an appropriately designed casting mold.
During the continuous casting of steel with plate molds there is furthermore known to the art a method which contemplates accommodating the taper of the hollow mold compartment between both of the narrow sides of the mold also during the casting operation upon change of the casting parameters. This method which is suitable for the casting of slab shapes cannot be employed when casting billet sections and square bloom sections as well as during casting in tube molds.
In order to avoid longitudinal fissures, especially edge fissures, and to reduce the danger of metal break-out with increased casting speed, it is further known in this field to limit the converging hollow mold compartment by means of walls having parabolic-shaped surfaces. The parabolic-shaped surfaces of the inner walls of the mold can also be bounded by step-shaped, planar surfaces, so that, viewed in the direction of travel of the strand, there are formed successive taper stages or regions, the degree of taper of which reduces in the direction of strand travel. At the region of the cast molten bath level or meniscus the hollow mold compartment is provided with parallel walls. This multiple-conical hollow mold compartment is designed for predetermined steel composition, casting speed and mold length. When casting steel charges of different composition and so forth, it is necessary to exchange such molds, thereby reducing the available production capacity of the continuous casting installation.